(1) Field of the Invention
The present invention relates to an image processing apparatus such as a copier, printer, facsimile machine or a multifunctional machine consisting of these. In particular, the present invention relates to an image processing apparatus which can prevent leakage of the information processed thereby.
(2) Description of the Prior Art
Conventionally, there have been copiers(e.g., digital copiers) which scan image data of originals, and once stores it into a nonvolatile memory such as a hard disk or the like and reads out the image data as appropriate from that memory so as to print it out. Such a copier will continue to hold the image data of previously scanned originals even after its printing out until other originals are scanned next and the data is overwritten on the hard disk. Therefore, if the hard disk is taken out from the machine body and the stored data is analyzed, the information of the previously scanned image data may leak out. So this problem has been crucial especially when confidential information and the like are involved.
To deal with this problem, according to the technique disclosed in Japanese Patent Application Laid-Open Hei 9 No. 223061, a confidential document mode is introduced, in which the image data will be erased as soon as the process of the image data is completed. In another technique disclosed in Japanese Patent Application Laid-Open Hei 9 No. 284572, the image data is adapted to be erased while the machine is idle.
However, the erasing process of image data takes a definite time. In particular, in order to clear the stored image data from a rewritable disk memory medium(such as a hard disk, MO, CD-RW, DVD-RW), it may take about 0.7 seconds for an A4 sized image or about 70 seconds for image data of 100 pages in a case of a hard disk, though the time differs depending on the amount of data and the type and features of hardware(the device).
Since writing and reading of image data cannot be implemented while image data erasing is being executed, it is impossible to perform image data erasing in parallel with other processes. Accordingly, if data erasing is actuated without consideration of the usage condition of the image processing apparatus, the next process cannot be started until the image data erasing is completed. This leads to lowering of the processing efficiency.